linux-kernel - [tip:sched/core] sched: Fix hotplug vs. set_cpus_allowed

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Date:	Thu, 22 May 2014 05:26:02 -0700
From:	tip-bot for Lai Jiangshan <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...nel.org,
	torvalds@...ux-foundation.org, peterz@...radead.org,
	srivatsa.bhat@...ux.vnet.ibm.com, rafael.j.wysocki@...el.com,
	toshi.kani@...com, ego@...ux.vnet.ibm.com,
	akpm@...ux-foundation.org, wangyun@...ux.vnet.ibm.com,
	tglx@...utronix.de, laijs@...fujitsu.com,
	paul.gortmaker@...driver.com
Subject: [tip:sched/core] sched: Fix hotplug vs. set_cpus_allowed_ptr()

Commit-ID:  6acbfb96976fc3350e30d964acb1dbbdf876d55e
Gitweb:     http://git.kernel.org/tip/6acbfb96976fc3350e30d964acb1dbbdf876d55e
Author:     Lai Jiangshan <laijs@...fujitsu.com>
AuthorDate: Fri, 16 May 2014 11:50:42 +0800
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Thu, 22 May 2014 10:21:31 +0200

sched: Fix hotplug vs. set_cpus_allowed_ptr()

Lai found that:

  WARNING: CPU: 1 PID: 13 at arch/x86/kernel/smp.c:124 native_smp_send_reschedule+0x2d/0x4b()
  ...
  migration_cpu_stop+0x1d/0x22

was caused by set_cpus_allowed_ptr() assuming that cpu_active_mask is
always a sub-set of cpu_online_mask.

This isn't true since 5fbd036b552f ("sched: Cleanup cpu_active madness").

So set active and online at the same time to avoid this particular
problem.

Fixes: 5fbd036b552f ("sched: Cleanup cpu_active madness")
Signed-off-by: Lai Jiangshan <laijs@...fujitsu.com>
Signed-off-by: Peter Zijlstra <peterz@...radead.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Gautham R. Shenoy <ego@...ux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Michael wang <wangyun@...ux.vnet.ibm.com>
Cc: Paul Gortmaker <paul.gortmaker@...driver.com>
Cc: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Cc: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>
Cc: Toshi Kani <toshi.kani@...com>
Link: http://lkml.kernel.org/r/53758B12.8060609@cn.fujitsu.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 kernel/cpu.c        | 6 ++++--
 kernel/sched/core.c | 1 -
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/kernel/cpu.c b/kernel/cpu.c
index a9e710e..247979a 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -726,10 +726,12 @@ void set_cpu_present(unsigned int cpu, bool present)
 
 void set_cpu_online(unsigned int cpu, bool online)
 {
-	if (online)
+	if (online) {
 		cpumask_set_cpu(cpu, to_cpumask(cpu_online_bits));
-	else
+		cpumask_set_cpu(cpu, to_cpumask(cpu_active_bits));
+	} else {
 		cpumask_clear_cpu(cpu, to_cpumask(cpu_online_bits));
+	}
 }
 
 void set_cpu_active(unsigned int cpu, bool active)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 44e00ab..86f3890 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5076,7 +5076,6 @@ static int sched_cpu_active(struct notifier_block *nfb,
 				      unsigned long action, void *hcpu)
 {
 	switch (action & ~CPU_TASKS_FROZEN) {
-	case CPU_STARTING:
 	case CPU_DOWN_FAILED:
 		set_cpu_active((long)hcpu, true);
 		return NOTIFY_OK;
--
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